Razor blades and methods of manufacture thereof



United States Patent US. Cl. 148-63 11 Claims ABSTRACT OF THE DISCLOSURE Coatings are formed on the cutting edge of steel razor blades by the steps of cleaning the cutting edge, applying to the cutting edge a thin layer of chromium of less than 400 Angstroms in thickness, preferably of less than 100 Angstroms, after which the blade is heat treated in a controlled oxidising atmosphere. The heat treating may be at a temperature of approximately 400 C. and at a pressure of approximately 10* torricelli.

The chromium content of the blades may be increased in the surface region of the cutting edge by a chromating process. Conversion of a substantial portion of the chromium on the cutting edge to chromium oxide may be effected by anodising, for example by means of a glow discharge or in a liquid electrolyte.

This invention relates to razor blades.

According to the present invention at least the surface region of at least the cutting edge or cutting edges of a razor blade comprise chromium oxide.

The provision of such a surface comprising chromium oxide is designed to impart improved properties to the razor blade by giving enhanced durability to the cutting edge or edges.

One method of providing the chromium oxide surface is first to coat with chromium which is thereafter oxidised. An alternative method is to coat the surface with chromium oxide thereby eliminating the oxidising step. Yet another method is to enrich the chromium content of at least the surface region of a stainless steel razor blade by a chromating process with subsequent oxidisation.

In greater detail, one method of manufacture is to clean the cutting edge or edges, thereafter applying a thin layer of chromium, for example, less than 400 Angstroms in thickness. A thickness of less than 100 Angtroms is preferred. The blade is next annealed to improve the bond with the coating and is then heat-treated in a controlled oxidising atmosphere. The chromium coating and subsequent heat treatment can be effected without impairing the cutting edge and in some circumstances may be efiected as a single operation.

Thereafter the blades may be provided with coatings or particles of materials to facilitate shaving, such as the already known or novel coatings referred to in the specification of Belgian Patent No. 504,784 of Apr. 5, 1963 in the name of Wilkinson Sword Limited. The heat treatment required to cure the polytetrafluoroethylene will in some cases be adequate to ensure adhesion between the vapour deposited chromium and the blade edge.

The method chosen for cleaning the blade should take account of the properties of the blade material, typical methods being by immersion in an organic solvent, for example, trichloroethylene, if necessary under ultrasonic vibration, with subsequent drying, by vapor degreasing in trichloroethylene, by glow discharge or by a brief anodic etching. If the latter method is used with an 3,480,483 Patented Nov. 25, 1969 aqueous solution of chromium trioxide, this can constitute the chromating process referred to above.

The selected method of coating the blade can likewise be chosen to 'be the most suitable for the material in question and examples of possible methods are by vapour deposition, by sputtering, possible with the sputtering direction in an ion beam, by electro-plating or by gas reaction.

Finally, it is necessary to effect controlled oxidation of the metal surface. This may be achieved by heat treatment in a controlled atmosphere in which the amount of oxygen present is strictly limited; for example the blade may be heated to 400 C. in air at a pressure of 10 torricelli. Another method is to anodise in a gaseous or liquid electrolyte; for example anodising may be by means of an air glow discharge at a low pressure, say a pressure of microns. A feature of the invention is that the amount of oxygen present during the oxidation process is strictly controlled.

Thus, considering the application of the process to stainless steels which can be used for razor blades, the process may typically involve vapour degreasing in trichloroethylene or chloroform, coating with chromium by vapour deposition, annealing in vacuum to bond the deposit to the edge, oxidising in a controlled atmosphere at temperatures up to 450 C. and applying a coating of polytetrafluoroethylene.

I claim:

1. The method of forming a chromium oxide coating on a cutting edge of a stainless steel razor blade comprising the steps of enriching the chromium content in the surface region of said cutting edge by a chromating process, and heat treating the cutting edge in a controlled oxidising atmosphere.

2. The method of forming a chromium oxide coating on a cutting edge of a steel razor blade comprising the steps of cleaning the cutting edge,

applying to the cutting edge a thin layer of chromium of less than 400 Angstroms in thickness, and

heat treating the blade in a controlled oxidising atmosphere to convert a substantial proportion of the chromium to chromium oxide.

3. The method according to claim 2, wherein said heat treating comprises heating to a temperature of approximately 400 C. in air at very low pressure.

4. The method according to claim 2, wherein said chromium is applied by vapour deposition.

5. The method according to claim 2, wherein said chromium is applied by sputtering.

6. The method according to claim 2, wherein said controlled oxidising atmosphere is at a pressure of approxi mately 1O torricelli.

7. The method according to claim 2, wherein said coating of chromium is of less than 100 Angstroms.

8. The method according to claim 2, comprising the further step of applying to the chromium oxide coating a coating of polytetrafluoroethylene.

9. The method of forming a chromium oxide coating on a cutting edge of a steel razor blade comprising the steps of cleaning the cutting edge,

applying to the cutting edge a thin layer of chromium of less than 400 Angstroms in thickness, and anodising the chromium coating to convert a substantial proportion of the chromium to chromium oxide.

10. The method according to claim 9, wherein the anodising is effected by means of a glow discharge in the presence of a restricted amount of oxygen.

11. The method according to claim 9, wherein the anodising is eflected in a liquid electrolyte.

References Cited UNITED STATES PATENTS 4 FOREIGN PATENTS 6/1949 Canada. 4/ 1967 Great Britain.

5 RALPH S. KENDALL, Primary Examiner US. Cl. X.R. 

